Endoscopic surgical instruments are often preferred over traditional open surgical devices since a smaller incision tends to reduce the post-operative recovery time and complications. Consequently, significant development has gone into a range of endoscopic surgical instruments that are suitable for precise placement of a distal end effector at a desired surgical site through a cannula of a trocar. These distal end effectors engage the tissue in a number of ways to achieve a diagnostic or therapeutic effect (e.g., endocutter, grasper, cutter, staplers, clip applier, access device, drug/gene therapy delivery device, and energy device using ultrasound, RF, laser, etc.).
Anastomosis is the surgical joining of separate tissue sections. Typically, an anastomosis procedure follows surgery in which a diseased or defective section of hollow tissue is removed and the remaining end sections are to be joined, however hemorrhoidal or other tissue can also be anastomized. Depending on the desired anastomosis procedure, the end sections may be joined by either circular, end-to-end, or side-to-side organ reconstruction methods.
In a circular anastomosis procedure, the two ends of the tissue sections are joined by means of a stapling instrument which drives a circular array of staples through each tissue section and simultaneously cores any tissue interior of the driven circular array of staples to create a tubular passage. Known circular staplers typically include an anvil head that is positioned adjacent to a staple holding component. Opposed end portions of the tissue to be stapled are clamped between the anvil head and the staple holding component, and the clamped tissue is stapled by driving one or more staples from the staple holding component so that the ends of the staples pass through the tissue and are deformed by the anvil head. An annular knife can be concurrently or subsequently advanced to core tissue to create a tubular passage.
One drawback to current circular stapling devices is that a large force is required to effect firing, and the force changes throughout the course of the firing stroke. Most current circular stapling devices utilize a hand-squeezed trigger. The load is low during early portions of the stroke when the staples are advancing out of the cartridge and piercing the tissue. Once the staples enter into the anvil pockets, the resistance and load rises rapidly as the staple legs buckle. Then the resistance and load drop down and rise again as the staples are formed. In contrast, the operator has maximum effective strength at the early and mid-stages of the firing stroke, whereas the effective strength is minimized during the final stages of closure. The large force necessary to effect firing, as well as the variations in the force, can often exceed the surgeon's hand strength and could potentially result in binding or other malfunctions that may occur when an unexpectedly higher force is required.
The large force required to effect firing can also interfere with the flexibility or adjustability of the shaft. Currently, the staple holding component can be pivotally coupled to the shaft, or the shaft can be flexible to allow the shaft to travel through a curved pathway. The transfer of force from the handle to the staple holding component can necessarily interfere with the pivoted or curved orientation of the shaft, potentially causing it to straighten.
Accordingly, there remains a need for methods and devices for actuating and/or articulating a circular stapler, and in particular for methods and devices that require a low force to effect actuation and/or articulation of a circular stapler.